Great plains is the broad interior are of north america that used to be grasslands
The soil layers are, in order: dirt, humus, rock. So the answer is D.
Hydrogen is used by plants which combine it with carbon during the photosynthesis process and release oxygen into the atmosphere which is used by all living beings.
The theory of continental drift by Alfred Wegener states that all land masses were originally united
in a single supercontinent known as Pangaea (250 million years ago). He shows
evidences like continental fit, similarity of rock sequences, glacial till and
striations, fossils (cynogathus-land reptile, lystrosaurus-land reptile,
mesosaraus-freshwater reptile, glossopteris-fern plant) to support his theory but
what was lacking is that it lacked a mechanism to explain HOW the continents
moved apart. But Harry Hess, a geologist and Navy submarine commander during
WWII <span>brought up a new
evidence to add in support of Wegener’s theory: the idea of seafloor spreading and magnetic reversals.</span>
